Inflorescence Size Research Articles

A comparative study on the reproductive success of two rewarding Habenaria species (Orchidaceae) occurring in roadside verge habitats

BackgroundMost orchid species have been shown to be severely pollination limited, and the factors affecting reproductive success have been widely studied. However, the factors determining the reproductive success vary from species to species. Habenaria species typically produce nectar but exhibit variable fruit set and reproductive success among species. Here, we investigated the influence of the flowering plant density, inflorescence size, breeding system, and pollinator behaviour on the reproductive success of two rewarding Habenaria species.ResultsOur observations indicated that Habenaria limprichtii and H. petelotii co-occur in roadside verge habitats and present overlapping flowering periods. Both species were pollination limited, although H. limprichtii produced more fruits than H. petelotii under natural conditions during the 3-year investigation. H. petelotii individuals formed distinct patches along roadsides, while nearly all H. limprichtii individuals clustered together. The bigger floral display and higher nectar sugar concentration in H. limprichtii resulted in increased attraction and visits from pollinators. Three species of effective moths pollinated for H. limprichtii, while Thinopteryx delectans (Geometridae) was the exclusive pollinator of H. petelotii. The percentage of viable seeds was significantly lower for hand geitonogamy than for hand cross-pollination in both species. However, H. limprichtii may often be geitonogamously pollinated based on the behaviours of the pollinators and viable embryo assessment.ConclusionsIn anthropogenic interference habitats, the behaviours and abundance of pollinators influence the fruit set of the two studied species. The different pollinator assemblages in H. limprichtii can alleviate pollinator specificity and ensure reproductive success, whereas the more viable embryos of natural fruit seeds in H. petelotii suggested reducing geitonogamy by pollinators in the field. Our results indicate that a quantity-quality trade-off must occur between species with different breeding strategies so that they can fully exploit the existing given resources.

<strong><em>Lymania involucrata</em> (Bromeliaceae: Bromelioideae), a new ornamental species from Bahia, Brazil</strong>

The authors describe, discuss, and illustrate Lymania involucrata, a new ornamental species from the Atlantic Forest in the municipality of Igrapiúna, Bahia, Brazil, here considered a critically endangered species. The new species is morphologically related to L. brachycaulis but clearly diffe According to Sousa rs from it by the well-developed, involucral primary bracts and the distinct shape and size of inflorescence, primary branches, and flowers. A map of the distribution of the species and taxonomic comments are presented.

Morphological Variability of Leonurus quinquelobatus (Lamiaceae): Environmental and Resource Potential Perspective

The influence of the environment on the studied characteristics can be determined when growing genetically similar plants in different environmental conditions. The medicinal plant Leonurus quinquelobatus Gilib. (five-bladed motherwort) belongs to a group of plants that are most responsive to changes of environmental conditions. Plants were grown from genetically uniform seeds in trial plots in three different southern regions of West Siberia (Kemerovo, Novosibirsk, and Kamlak Village, Altai Republic). Measurements were performed for 10 model live plants in each trial plot three times per growing season during three years. Variability of 23 vegetative and generative traits was studied based on linear, quantitative, and calculated data. The following traits correlated significantly with the phase of development: height of plant; branching of first-order shoots; length of the generative parts; inflorescence size share in plant height; width of generative part of the shoot; number of generative internodes of the first-order shoot; numbers of internodes with buds, flowers, and fruit; flowering index; fruiting index. The following traits changed significantly in different habitats: plant height; branching of first-order shoots; all generative traits studied. The branching and flowering indices changed due to the interaction of factors. The projection area of the aboveground part and the number of third-order shoots on a second-order shoot did not depend significantly on either the development phase or the growing region. For further research, the number of morphological traits under study could be reduced depending on the aims of the research

Improving architectural traits of maize inflorescences

The domestication and improvement of maize resulted in radical changes in shoot architecture relative to its wild progenitor teosinte. In particular, critical modifications involved a reduction of branching and an increase in inflorescence size to meet the needs for human consumption and modern agricultural practices. Maize is a major contributor to global agricultural production by providing large and inexpensive quantities of food, animal feed, and ethanol. Maize is also a classic system for studying the genetic regulation of inflorescence formation and its enlarged female inflorescences directly influence seed production and yield. Studies on the molecular and genetic networks regulating meristem proliferation and maintenance, including receptor-ligand interactions, transcription factor regulation, and hormonal control, provide important insights into maize inflorescence development and reveal potential avenues for the targeted modification of specific architectural traits. In this review, we summarize recent findings on the molecular mechanisms controlling inflorescence formation and discuss how this knowledge can be applied to improve maize productivity in the face of present and future environmental challenges.

Reproductive development and pollen-stigma interaction in sunflower plants receiving boron deficient and toxic supply

To study the effect of boron deficiency and toxicity on the reproductive development and pollen-stigma interaction in sunflower (Helianthus annuus var. Sungold), plants were raised in sand culture under glass house condition till maturity at 0.033 (deficient), 0.33 (sufficient) and 3.3 (toxic) mg B L−1 supply. The effect of deficiency and toxicity of boron on the number, size and weight of inflorescence, anther size, pollen producing capacity (PPC) of an anther and pollen viability were determined. Enzymes peroxidase, acid phosphatase and esterase and protein were cytochemically localized on the stigmatic surface of disk floret. As compared to control plants (0.33 mg B L−1 supply) development of inflorescence was not only delayed but also poor under boron deficiency and toxicity. Pollen grains produced under boron deficiency and toxicity had reduced size with low viability. Histochemical localization of proteins showed marked decrease in concentration on the stigmatic surface of plants receiving deficient and toxic boron supply. Cytochemical localization of peroxidase enzymes on the stigmatic surface showed increased activity whereas a decrease in acid phosphatase and esterase activity was observed suggesting poor pollen stigma interaction under boron stress condition which might be the cause of poor fertilization.

A new endemic and critically endangered species of Butia (Arecaceae) with comments on morpho-anatomical novelties in the genus

Butia buenopolensis, a new dwarf Arecaceae species, is described. Butia buenopolensis occurs in the Serra do Cabral mountain range in Buenopolis municipatility, Minas Gerais, Brazil. Despite its diminutive size, it has arched yellowish-green leaves and pinnae not as narrow as the species of the grass-like Butia. The new species is closely related to B. archeri, based on morphology, phenology (flowering time) and habitat. They differ in leaf anatomy, plant size, color and size of inflorescence. Some novelties in Butia flower morphology, such as striated cuticle of anthers, functional staminodes presenting evidence of secretory activity, raphides on the petals of pistillate flowers and the cappilinection adhesion of petal margins, were introduced here and suggested as a new approach for future taxonomical and evolutionary studies of this genus. The isolated and small groups of fibers in the mesophyll and a non-vascular fiber bundle connected to the adaxial epidermis in the leaf midrib have not been found in any other Butia so far. The one population recorded for the new species is restricted to an area near the limits of Serra do Cabral State Park, clearly vulnerable to different forms of anthropic pressure. So, it is strongly recommended an extension in area of Serra do Cabral State Park to include the B. buenopolensis range of occurrence within its borders.

Новый вид Corydalis (Fumariaceae) из Синьцзяна (Китай)

A new species Corydalis nodosa Mikhailova (sect. Strictae (Fedde) Wendelbo) is described from NW China, Xinjiang, Tian Shan mountain system, Dzharges ridge. The new species differs from C. tianshanica Lidén by its larger size, shorter pedicels, and shorter spur; from C. laxifloraLidén by biternate leaves, a short racemose inflorescence, missing bracteoles, and smaller size. From the two above-mentioned species, it differs by nodose last year’s stems.

Componentes do rendimento e composição química de grãos de genótipos de Salvia hispanica L. cultivados no Oeste do Paraná sob diferentes densidades populacionais

O estudo teve o objetivo de comparar diferentes densidades populacionais de cultivo para genótipos de chia, ChiaSE e ChiaSB, para atributos de importância agronômica e composição química dos grãos. O experimento foi realizado em janeiro/maio de 2019 no município de São Miguel do Iguaçu, Paraná. O experimento foi conduzido em blocos casualizados com três repetições em esquema fatorial, testando-se os genótipos ChiaSE e ChiaSB cultivados com 40, 50, 60, 70 e 80 mil plantas.ha-1. Variáveis morfo-agronômicas e da composição química dos grãos foram avaliadas para todas as unidades experimentais. Os resultados revelaram que os genótipos emitem ramos no mesmo período e independente da população, iniciando o florescimento aos 90 dias. Detectou-se que a população tem influência sobre da altura das plantas, ocorrendo aumento da estatura com o incremento da densidade de plantas, ocorrendo acamamento para cultivos com 80 mil plantas.ha-1. Verificou-se também que o aumento populacional para ChiaSE resulta em maior número de ramos e inflorescências por planta em relação a ChiaSB, sem ocorrer mudanças do tamanho das inflorescências. A ChiaSE é mais produtiva comparado a ChiaSB, sendo que 70 mil plantas.ha-1 é a mais recomendada para produção de grãos. Os grãos de ChiaSE e ChiaSB são ricos em proteínas e lipídeos, sendo que a população não tem efeito sobre a composição. Enfim, conclui-se que a chia pode ser cultivada em local de baixa altitude do Oeste do Paraná, sendo que ChiaSE é o genótipo mais promissor, e responde ao aumento da população sem influenciar a composição química dos grãos.

Reproductive ecology of Saxifraga florulenta, a monocarpic perennial paleo-endemic of the Alps

Saxifraga florulenta is a monocarpic species endemic to SW Alps, whose reproductive biology is still unknown. Its knowledge may provide useful information on how the species may face the global warming. In this study, we investigated the plant–pollinator interactions and the mating system of the plant. We described the phenology of the inflorescences, we evaluated the type of pollinators, we verified self and cross-pollination and lastly we quantified the reproductive success of the plants. In spite of the low visitation rate of pollinators, S. florulenta shows high fruit set and seed set. The plant exhibits a prolonged flowering period and has a definite inflorescence, characterized by a sequential blooming bearing both female- or male-phase flowers at the same time; in addition, flowers show a delayed maturation and movement of stamens. These floral and inflorescence traits lead to a mixed reproduction mode which guarantees reproductive success by adopting the “best of two worlds” strategy. The species maximizes its resource investment by having inflorescence size and number of flowers directly related to plant size, whilst fruit and seed set as well as seeds per flower did not show any statistically significant relationship with plant size.

<p><strong>A new species of <em>Werauhia</em> (Bromeliaceae: Tillandsioideae) from the Brazilian “Hylaea”</strong></p>

The authors describe and illustrate Werauhia hylaeana, a new species of Tillandsioideae (Bromeliaceae) from the Amazonian “Hylaea” of Brazil. It is related to W. gladioliflora, but differs in its stature, leaf blade, and inflorescence size, in the shape of floral bracts, sepals, and petals. An identification key for the species of Werauhia reported to Brazil is presented, in addition to habitat and distribution data for the new species.

Multiple Loci Control Variation in Plasticity to Foliar Shade Throughout Development in Arabidopsis thaliana.

The shade avoidance response is a set of developmental changes exhibited by plants to avoid shading by competitors, and is an important model of adaptive plant plasticity. While the mechanisms of sensing shading by other plants are well-known and appear conserved across plants, less is known about the developmental mechanisms that result in the diverse array of morphological and phenological responses to shading. This is particularly true for traits that appear later in plant development. Here we use a nested association mapping (NAM) population of Arabidopsis thaliana to decipher the genetic architecture of the shade avoidance response in late-vegetative and reproductive plants. We focused on four traits: bolting time, rosette size, inflorescence growth rate, and inflorescence size, found plasticity in each trait in response to shade, and detected 17 total QTL; at least one of which is a novel locus not previously identified for shade responses in Arabidopsis. Using path analysis, we dissected each colocalizing QTL into direct effects on each trait and indirect effects transmitted through direct effects on earlier developmental traits. Doing this separately for each of the seven NAM populations in each environment, we discovered considerable heterogeneity among the QTL effects across populations, suggesting allelic series at multiple QTL or interactions between QTL and the genetic background or the environment. Our results provide insight into the development and variation in shade avoidance responses in Arabidopsis, and emphasize the value of directly modeling the relationships among traits when studying the genetics of complex developmental syndromes.

CHARACTERISTICS OF DAHLIA CAV. VARIETIES RESEARCHED UNDER CONDITIONS OF THE EXPOSITION AREA OF VINNYTSIA NATIONAL AGRARIAN UNIVERSITY

The results of studies on the use of decorative ornamental plants of flower and ornamental plants Dahlia Cav. in Vinnytsia Region at their level of adaptation to growing conditions have been presented. The assessment of the collection of the genus Dahlia Cav. at the exposition site of the Vinnitsa National Agrarian University, it has been determined that the collection is dominated by varieties of individual garden groups such as cactus, nymphae and decorative. In order to expand and replenish the collection of the genus Dahlia Cav the exhibition area VNAU conducted a selection of varieties that are representative of a set of indicators such as plant height, shape and size of inflorescences among the dahlia assortment. Dahlias are easy to grow and bring life to your garden with their intense color, strength, and ability to keep flowering until the first frosts. Dahlias like well-balanced and composted soil, and full sun. With 42 different species and thousands of cultivars, dahlias offer plenty of variety. Variations in color, flower form, size, and foliage make it easy to find one you'll love. The rich variety of their flower colors shapes and sizes added to their extensive blooming season, have turned dahlias into popular addition to our landscapes. There are thousands of varieties of dahlias and they are all classified by the shape, size and color of their flowers. Flowers can be very small in diameter. They offer an impressive range of colors such as pink, purple, red, scarlet, orange, yellow, white and can be stripped or tipped with another color. They can be single-flowering (orchid-flowering, anemone and collarettes) or double flowering (cactus, semi-cactus, formal or informal decorative dahlias, ball and pompons). Dahlias have wide height range. There are many different ways to use dahlias in the garden. Shorter dahlias mix well with annuals or shorter perennials, while taller varieties will grow well with perennials and ornamental grasses toward the rear or center of borders. Their lower stems tend to be unattractive and the plants are heavy (especially the large flowered dinnerplate types); so without staking, they tend to flop. Plant the smallest varieties in containers. Dahlia flowers are brightly colored. They can also look surprisingly good with grasses, as the contrast is total-big bright flowers against finely textured grasses. Good cutting dahlias tend to be the larger varieties because of their longer stems. Key words: dahlias, collection, garden group, flowering, container culture.

New species, Bulbophyllum trongquyetii (Orchidaceae) from Vietnam

Bulbophyllum trongquyetii is described as new for science from Vietnam. Detailed morphological description, illustration, data on distribution, and phenology are provided. Described species resembles B. nipondhii but differs in the bigger size of plant, longer inflorescence, and uniform yellow or reddish-orange flowers. It can be also compared with B. thaiorum and B. farreri but easily distinguished by the bigger size of plant and flowers, as well as smooth or sparsely papillose lateral sepals.

Вплив системи догляду за кроною на декоративність і довговічність рослин сортів Syringa vulgaris L.

Досліджено вплив способів обрізування крони рослин Syringa vulgaris L. на їхню декоративність і довговічність. Встановлено, що досягти найкращого результату можна тільки за регулярного догляду за кроною. Спонукає до цього, щонайперше, дихотомічне (несправжнє) гілкування, за яким кожна однорічна гілка продукує навесні два пагони з верхівкової пари бруньок та ще кілька – з бруньок, що розташовані нижче по осі цієї гілки. Отже, щороку загальна їхня кількість щонайменше потроюється. Коренева система не зможе за цей час збільшити в таких обсягах свою масу і фізіологічну активність, що корелятивно спричиняє значне зменшення розмірів пагонів і суцвіть. Якщо догляд був нерегулярний або відсутній, виникає потреба інтенсивного прорідження або кардинального омолодження крони. Доведено, що цими заходами можна поліпшити декоративність рослин, але на довговічність вони вплинуть негативно. Зумовлює це дві причини. Перша – запобігання ран внаслідок видалення гілок на кільце. Встановлено, що навіть 1,5-2,0-сантиметрові зрізи на стовбурі чи скелетних гілках ніколи не загояться, а за 10-15 років їхня деревина струхліє, утворивши порожнину. Деревина великих ран руйнується швидше, що призводить до виникнення дупел та повільного відмирання всієї рослини. Другою причиною вкорочення довговічності є раптово порушений функціональний корелятивний коренево-листковий зв'язок, що є наслідком різкого зменшення в омолодженій рослині надземної частини. Спочатку це призведе до сповільнення фотосинтезу (крона майже відсутня), а потім, корелятивно, й до затухання кореневого синтезу: через мізерне надходження асимілятів до коренів. Унаслідок цього загальна маса фізіологічно активної частини кореневої системи теж значно зменшиться, що негативно вплине на довговічність рослини загалом. Декоративність кущів через це з року в рік погіршується. Також встановлено, що до обрізування крони змушує й загущена посадка бузків. Для відновлення її декоративності спочатку варто видалити кволі рослини, а в решти – знизити крону приблизно на третину аби наблизити її до кореневої системи, що забезпечить рослинам фізичну витривалість та дещо внормує в них функціональний коренево-листковий зв'язок. Здійснити цей захід треба якомога раніше в часовому вимірі, бо, окрім згаданого, рослини почнуть страждати й від хвороб. Потужні гілки потрібно вкорочувати, а не вирізати на кільце, аби не нанести стовбурам і гілкам першого порядку великих ран. За такого підходу до обрізування крони бузки будуть декоративними й здебільшого випадків – довговічними.

Four new species in subsection Asterotricha for the genus Onosma L. (Boraginaceae) from flora of Iran

Onosma khorramabadensis, O. lorestanica, O. sahandica and O. kerendica are described and photographed as new species from Lorestan, Eest Azarbayejan and Kermanshah provinces of Iran. Based on Flora Iranica, all the new species can be placed in the sect. Onosma subsect. Asterotricha considering their stellate‐hairy tubercles on leaves.The first new species has some similarities to Onosma bilabiata and O. elwendica based on having accrescent and two connected calyx lobes, but can be distinguished by its stem leaves shape and size, elongate inflorescence and more characters. O. lorestanica is close to O. elwendica by having spathulate leaves shape and nearly same fruiting calyx length; however it differs by its dense short capitate cyme in flowering time, tubercles density and rays arrangements on the tubercles. O. sahandica can be also close to O. bilabiata and O. elwendica for its fruiting calyx length and corolla color, but differs by having free calyx lobes and not accrescent at fruiting time. O. kerendica is related to O. cardiostegia by its habit and inflorescence shape, but can be distinguished by length of lowest bracts, its inflorescence size in fruiting time, pedicel length and filaments attachment place.The recent introduced species, Onosma zagrica (Dehshiri, 2018) should be classified into subsection Asterotricha instead of being in subsection Onosma according to its description and type specimen examination.Distribution map, micrographs of details of important characteristics and a diagnostic key are presented.

<p><strong><em>Salix aegaea</em></strong><strong> (Salicaceae), a new species from island of Ikaria (Greece)</strong></p>

A new species of willow from Ikaria Island (Greece), named Salix aegaea, is described and illustrated. For the leaf shape, as well as for the hairy ovary, capsule and base of stamina filaments, it shows close relationships with the species belonging to S. apennina group. It is morphologically well differentiated in several features regarding the shape and size of branches, leaves, inflorescences, floral bracts, ovaries, stamens and capsules, as well as the structure of leaf epicuticular waxes and hairs. Considerations on its ecology, chorology, leaf micro-morphology, conservation status and the identification keys including the allied species are also provided.

Contrasting population genetic structure of two sympatric species of Anthurium (Araceae) along elevation in an Andean mountain forest

AbstractThe topography of the tropical Andean forest is steep, resulting in physical conditions that change with the elevation, thus driving a high turnover of insect pollinator species over short distances, which may lead to localized gene dispersal, promoting genetic divergence between plant populations distributed along the elevation gradient. In this study, we characterized the population genetic structure of Anthurium caucanum and A. panduriforme, two closely related species that coexist along the elevation gradient in the Andean forest but differ in inflorescence size and abundance of flower visitors. The sampling of both species covered seven elevation bands, from 2,200 to 2,900 MASL. Five microsatellite loci were used to genotype the sampled individuals. Our results indicated that heterozygosity was high for both species. Genotypic richness was significantly lower for A. caucanum (G/N = 0.45) compared with A. panduriforme (G/N = 0.88), while population differentiation was strong for A. caucanum (Fst = 0.23) but low for A. panduriforme (Fst = 0.03). Assignment analysis suggested a low rate of immigration events for A. caucanum populations and a high gene flow between A. panduriforme populations. Based on the seed production of bagged inflorescences, A. caucanum demonstrated the ability to self‐pollinate, while A. panduriforme was considered self‐incompatible. In addition, genotypic richness decreased with elevation for A. caucanum. In summary, the contrasting population genetic structure of the two Anthurium species along the elevation gradient appear to be the result of different gene flow rates, mating systems, and life‐history traits, such as clonal growth, flowering phenology, and density.Abstract in Spanish is available with online material.

The effect of weather conditions and application of mineral fertilizers on quality indicators of Callistephus chinensis (L) Nees

With the development of modern floral business, Callistephus chinensis (L.) Nees is among the top three of the most popular crops, yielding only chrysanthemum and calendula in commercial cultivation. This is one of the most widespread seasonal decorative annual flower crops, which is beautifully cultivated in open ground, pots and bouquet flowers. The researches presented in the article were conducted in order to determine the influence of weather conditions during the growing season of C. chinensis on the research sites of the educational scientific-production complex of the Sumy National Agrarian University (Northeast Forest-steppe of Ukraine) and the effectiveness of the application of various norms of complex mineral fertilizers, introduced at the planting of seedlings into open ground, on the processes of growth, flowering and other qualitative characteristics of the five varieties. During the growing season, the climatic conditions of the region of conducting research, variety characteristics, and also the variability of the parameters of height, number and diameter of C. chinensis inflorescences of the varieties 'Olenka', 'Leleka', 'Litnia Nich', 'Tsarivna' and 'Yabluneva' were influenced by variability mode of mineral nutrition. Weather conditions of vegetation have an impact on the number and size of inflorescences. According to research results, it has been established that there is a certain relationship between the weather conditions of the year and the number of inflorescences. So, the increase in the amount of precipitation during the growing season contributes to the development of the vegetative mass, but also negatively affects the formation of the number of inflorescences C. chinensis. For most varieties, the optimal conditions for the development of the generative sphere were the normal conditions for moisture of the year, and for the 'Litnia Nich' variety it was dry. The greatest increase in height when fertilizing compared to control was observed by the variety 'Tsarivna' (15.9 %), the smallest - by the variety 'Olenka' (2.0 %). The formation of inflorescences of greater diameter by the plants of the varieties 'Olenka', 'Litnia Nich' and 'Tsarivna' was observed in 2016, and by the 'Leleka' and 'Yabluneva' varieties in 2017. For most varieties in 2015, the diameter of inflorescences was the smallest. Studies have shown that weather conditions do not have a significant effect on the diameter of inflorescence, unlike mineral nutrition. The diameter of the inflorescences was the highest in comparison with the control by the variety 'Olenka' (18.3%), the smallest - by the variety 'Tsarivna' (1.1 %). The most valuable morphological and decorative features of C. chinensis plants of the five varieties under study were formed according to the norms of complex mineral fertilizers (nitroamofoska) 6.0 g/m2. The further increase of norm was not appropriate.

Disporum nanchuanense (Colchicaceae), a new species from Chongqing, China.

Disporum nanchuanense (Colchicaceae), a new species from Jinfo Mountain National Nature Reserve, Nanchuan District, Chongqing, China, is described and illustrated. It is similar to D. longistylum and D. megalanthum, but differs from the former in its stem branched type, tepals colour and size, stamens and pistil size; and it differs from the latter in inflorescence position, tepals shape, stamens position, pistil position and size. Meanwhile, the new taxon is assessed as Vulnerable (VU D2), according to the IUCN Red List criteria. Furthermore, an identification key to all Chinese species of Disporum is provided.

Диагностические признаки представителей рода Robinia L. по генеративным показателям в интродукционных популяциях

Promising forms of various species of the genus Robinia L., which are of great interest for enriching the gene pool of cultivated woody plants in arid regions. Genetic diversity is an important condition for the ability of populations to adapt to environmental changes. The higher the genetic heterogeneity, the greater the ability of the species to adapt to changing environmental conditions. The aim of the research is to inventory the species and form diversity of introduced Robinia populations and develop their diagnostic features based on the study of the structure and development of generative organs. The objects of research were introduced populations of different species and forms of the genus Robinia: R. adhesive-R. viscosa Vent.; R. neomexicana – R. neomexicana A. Gray; R. liegacy – R. pseudoacacia L., which grow in a cluster collectible parts FNTS Agroecology Russian Academy of Sciences, cadastre №34:34:000000:122, 34:34:060061:10. The results of the inventory collection funds has allowed to establish that the parental lines FNTS Agroecology wounds there are forms Robinia pseudoacacia and Robinia neomexicana, differing significantly from the typical representatives (Robinia neomexicana: R. neomexicana f. pale pink, R. neomexicana f. pale purple; Robinia pseudoacacia R. pseudoacacia f. postseconda). They are represented by large introduced populations (age 15 years), maintaining the number of which is due to natural vegetative and generative methods of reproduction. Analysis of natural distribution areas revealed that The most polymorphic species is considered to be Robinia neomexicana Grey (Robinia neomexicana Grey). In Russia it is often cultivated and is described, entitled Robinia lush (R. luxurians (Dieck) S. K. Schneid.). Developed diagnostic features characteristic of the selected forms and typical representatives of different species of the genus Robinia. Among them: the color of the Corolla and calyx, calyx structure, pubescence, the presence of a wing on the fruit, fruit size, generative axis of inflorescences, the average size of inflorescences, the number of inflorescences on the shoot, the duration of flowering terms. An important diagnostic feature in the identification of species of the genus Robinia is the structure of the calyx. The measurements showed that only Robinia pseudoacacia has fully fused upper sepals (adaxial sinus is not more than 0.3-0.6 mm). Cups R. neomexicana and R. viscosa and even R. pseudoacacia f. postseconda sometimes have distinct adaxial sinus to 4.5 mm. the Size of the flowers and the average number of flowers per inflorescence differs slightly. So, the average number of flowers varies from 20.5 units (Robinia neomexicana) to 22.3 (R. neomexicana f. pale purple). The sizes of inflorescences and the number of inflorescences on a shoot (during spring mass flowering) significantly differ. Fruits of R. viscosa Vent., R. neomexicana A. Gray (including forms) have side seams of equal width (wing absent). In addition, the fruits of R. pseudoacacia and its late-flowering form are always glabrous, the fruits of R. neomexicana A. Gray and its forms are bristly, and the fruits of R. viscosa Vent. - glandular-bristly (sticky in the immature state). The features of the structure and development of generative organs are analyzed, the seed productivity and fruit productivity of various species and forms of the genus Robinia are determined. It was revealed that the highest generative potential in arid climate has R. pseudoacacia and its forms, and the lowest – representatives of R. viscosa. A high percentage of set seeds (number of ovules/number of set seeds) was observed in R. pseudoacacia and its late-flowering form (more than 70%). Representatives of R. viscosa Vent had a low percentage of set seeds. and R. neomexicana A. Gray f. pale purple. The setability of seeds of typical representatives of R. neomexicana A. Gray was more than 60%. It was revealed that the most abundant and long - flowering species in arid conditions of the Lower Volga region is R. viscosa Vent. Widespread in the culture were two species: R. pseudoacacia L. and R. viscosa Vent. Robinia pseudoacacia, which has the largest range of natural distribution, has a wide range of adaptive capabilities and is easier to adapt to new conditions of existence in the process of introduction. This advantage allowed R. pseudoacacia to receive the widest distribution in culture not only in North America, but also in Russia. The second kind is R. viscosa Vent. it has the narrowest area of natural distribution, however, high decorative properties and, as a consequence, the active use of this species in the objects of gardening, allowed to significantly expand the area of its secondary distribution in North America, Europe and southern regions of Russia. Clustering of the main diagnostic signs revealed the belonging of the selected forms to a particular species, which is confirmed by the results of correlation analysis.